I've got a couple of the reports from the 1960s when the U. S. Army tested various lubricants in the Arctic. The M14 was among the test platforms. Based on those reports and other Army documents I've read, here's what I've added to the draft of the Third Edition of M14 Rifle History and Development:
"Cold Climate Care - For temperatures below freezing, all moisture and excess lubricant must be removed to keep the rifle working properly. In extensive arctic testing in the winter of 1968, the U. S. Army found the M14 malfunctioned 137 times out of 30,000 rounds fired (0.5 %) using five unlubricated rifles in ambient temperature ranging from 35 degrees Fahrenheit to - 58 degrees Fahrenheit. Among this set of five rifles, the most common malfunction was the failure of the bolt to lock open (44 of 137 instances). When LSA lubricant (then MIL-L-46000A) was used in the same test, the malfunction rate dropped to 23 malfunctions in 30,000 rounds fired (0.07 %) with another set of five M14 rifles. Each rifle was field stripped and cleaned every 1000 rounds during the test. LSA lubricant is no longer available in the military supply system.
The U. S. Navy prescribes a light coat of the synthetic blend, Cleaner Lubricant Preservative (CLP), in subzero temperature. The Mk 14 Mod 0 operator manual states CLP will provide adequate lubrication between 0 and - 35 degrees Fahrenheit in areas where grease is normally applied with the exception of the bolt roller. Regardless, it is best to keep the rifle outside in the cold air in such conditions. Without risking loss of life or limb, cover the rifle with cover (poncho, blanket, tarp, etc.) to protect it from snow or ice. If the rifle is brought into a heated space, do not clean it until the rifle has reached room temperature at which time it can be thoroughly cleaned of all moisture."